Constraining A4 leptonic flavour model parameters at colliders and beyond

Lukas Heinrich,Holger Schulz,Jessica Turner,Ye-Ling Zhou

doi:10.1007/jhep04(2019)144

Abstract

The observed pattern of mixing in the neutrino sector may be explained by the presence of a non-Abelian, discrete flavour symmetry broken into residual subgroups at low energies. Many flavour models require the presence of Standard Model singlet scalars which can promptly decay to charged leptons in a flavour-violating manner. We constrain the model parameters of a generic A4 leptonic flavour model using a synergy of experimental data including limits from charged lepton flavour conversion, an 8 TeV collider analysis and constraints from the anomalous magnetic moment of the muon. The most powerful constraints derive from the MEG collaborations’ limit on Br(μ → eγ) and the reinterpretation of an 8 TeV ATLAS search for anomalous productions of multi-leptonic final states. We quantify the exclusionary power of each of these experiments and identify regions where the constraints from collider and MEG experimental data are complementary.

Highlights

Sum-rules which will be testable at upcoming long (T2HK and DUNE) [2, 3] and medium (JUNO) [4] baseline neutrino oscillation experiments
To do so we apply a synergy of experimental data ranging from the reinterpretation an 8 TeV collider analysis to applying limits from charged lepton flavour violating (CLFV) processes determined by the MEG collaboration
As detailed in table 6, of the 3045 (34.8%) points which cannot be excluded by MEG, we found 378 of those points (12.4%) can be conservatively excluded by a combination of Higgs width, Higgs-scalar mixing and the ATLAS analysis

Summary

Introduction

Sum-rules which will be testable at upcoming long (T2HK and DUNE) [2, 3] and medium (JUNO) [4] baseline neutrino oscillation experiments. An alternative possibility was proposed in the work of [54], where the cross-coupling between the flavons of the neutrino and charged lepton sector may slightly break the Abelian residual symmetries and thereby provide the needed deviation from exact TBM mixing in the context of an A4 flavour model. To do so we apply a synergy of experimental data ranging from the reinterpretation an 8 TeV collider analysis to applying limits from charged lepton flavour violating (CLFV) processes determined by the MEG collaboration.

Objectives

Results

Conclusion